This invention relates to refractory compositions, and more particularly, it relates to moldable refractory compositions containing ceramic fibers having high resistance to molten aluminum alloys.
There are many commercially available refractory products or compositions which are designed for use with molten aluminum applications. These products include dense refractory brick, castables and plastic ramming mixes. Also available are light-weight insulating castables. These products contain additives which reduce reactions between the refractories and molten aluminum alloys. For example, LaBar U.S. Pat. No. 4,088,502 discloses a corrosion resistant castable refractory comprised of calcium aluminate, zinc borosilicate frit and fused silica. Lobaugh U.S. Pat. No. 2,516,892 discloses a refractory concrete which uses calcium aluminate cement, a refractory aggregate and an insoluble frit. Hofmann U.S. Pat. No. 4,060,424 discloses a ramming or gunning cement using boric acid and a low temperature softening glass or frit. Talley et al U.S. Pat. No. 4,126,474 discloses a phosphate-bonded alumina or alumino-silicate refractory for lining aluminum-melting furnaces and other containers for molten aluminum including 0.5 to 30 wt.% BaSO.sub.4. U.S. Pat. No. 4,174,331 discloses a refractory moldable composition which, upon drying, sets up to refractory shapes which are strongly adherent to the molding surfaces and are essentially crack-free, contains about 45 to about 65% of a liquid vehicle, such as water; about 21 to about 26% ceramic fiber; about 7 to about 30% finely divided silica; and sufficient adhesion enhancing agent to impart from about 18 to about 50 grams per square centimeter adherence to steel.
Yet in spite of these disclosures there is still a great need for a refractory composition having improved properties and which has a high level of resistance to molten aluminum.